Thanks Alan and Jim.
The top wire is doubled already...two wires 1m apart, with the ends joined.
I'm thinking of adding a third wire, if I can get it spaced far enough away
from the other two. I have plans to get another 1m at the feed point, but
I'm really running out of space!
The coil is wound on a low-loss polyethelyne former and I measured the Q to
be about 230. I've been quietly collecting bits on e-bay and I hope to have
a 400W tx available for the winter...that's a 3dB increase!
73,
Dave G3WCB IO91RM
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Alan Melia
Sent: 05 July 2006 23:07
To: [email protected]
Subject: LF: Re: LF loading coils <Litz>
Hi Dave if you double up your top wire and increase the capacity to 700pF
you might half the ground loss and double the ERP for the same power. If you
can get another 3m height on the feed point you will double the radiation
resistance and double the ERP again for the same aerial current.
There may be constraints but there is a lot more to be had in this area of
aerial development.
Cheers de Alan G3NYK
----- Original Message -----
From: Dave G3WCB <[email protected]>
To: <[email protected]>
Sent: 05 July 2006 22:33
Subject: LF: LF loading coils <Litz>
> Dear Gary, LF.
>
> I have just finished rewinding my loading coil. The original 3.2mH coil
was
> wound with 150 turns of 2.5mm cross-sectional area pvc covered solid
copper
> wire,(i.e. mains cable inner) The coil is 300mm dia and 500mm high, and
the
> antenna is a "Tee" at 6m with a 60m top. The antenna capacity to ground is
> about 390 pF.
>
> I rewound it with Litz wire of about the same cross-sectional area, and
got
> an antenna current increase of 15%. Not much, but every little helps.
>
> I haven't tried a short, fat loading coil yet, but the indications are
that
> short fat coils have lower losses.
>
> 73, Dave G3WCB IO91RM
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of James Moritz
> Sent: 05 July 2006 22:09
> To: [email protected]
> Subject: LF: Re: LF loading coils
>
>
> Dear Gary, LF group,
>
> ...But there is another justification for making a high-Q loading coil,
and
> that is power dissipation. If you are trying to run 1kW into a small
> antenna, it isn't hard to end up with a few hundred watts dissipated in
the
> loading coil if this has mediocre Q. This would only reduce the radiated
> signal by about 1dB or so compared to a perfect, zero-loss loading coil,
but
> it would certainly make the coil get warm! A big, high Q coil dissipates
> less power in the first place, and has more surface area to dissipate the
> heat, too.
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
> ----- Original Message -----
> From: Gary - G4WGT <[email protected]>
> To: <[email protected]>
> Cc: LW Wave <[email protected]>
> Sent: Wednesday, July 05, 2006 8:11 PM
> Subject: LF: RE: Re: LF loading coils
>
>
> > Hi Alan & Steve,
> >
> > You made almost identical comments.
> >
> *****************
> >
> > So I will give that idea a "MISS"
> >
> > Thanks to you both for your comments.
> >
> > 73
> >
> > Gary - G4WGT.
> >
> >
> >
>
>
>
>
>
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